Roman blinds offer the best window coverage but their complex manufacturing process means that they are not the most economical option. They do, however, add class to any room.

The feature fabric, with its thermal lining, is made to the finished width of the window, so if the blind is mounted inside the window recess it will be made to the narrowest width within the recess, less 1cm for a clearance fit.

As long as the window is nice and square the blind will block a considerable amount of light due to its close fit, making it the best blackout of all the blinds available.

If the blind is mounted on the outside of the recess we recommend allowing 4cm all around the window. The wider the blind the more light will be blocked, but remember that the fabric will stand off the wall a little due to the 3cm depth of the headrail on which the fabric is mounted.

For this reason there is little to be gained from an outside-mounted blind over a good fitting inside-mounted roman in a nice square window.

Blackout roller blinds are a popular choice since they are also one of the most economical options. Blackout fabrics are coated with a rubberised backing that also offers a thermal barrier, as with the Roman blind.

The brackets and controls are mounted at both ends of the barrel so 30mm of fabric is lost to accommodate them. This will inevitably allow light to creep around the sides of the blind, but it will be more than adequate to do the job unless you are a very light sleeper.

If that is the case it would be worth considering mounting the blind on the outside of the recess, making the blind wider than the window opening.

Vertical blinds have a small offering of blackout fabrics. Like the roller blind fabrics, vertical blinds have the same make-up, with the rubberised backing providing the blackout, and it also provides thermal properties.

The strips of fabric (technical name louvres) hang from a horizontal headrail, and of all the blinds this is the least effective at blocking light.

When the blind is closed the louvres overlap, allowing a little light to seep through. In addition, the two end louvres are set back from the end inside recess walls, along with a clearance gap under the louvres to allow the blind to rotate freely from the windowsill.

When you add these together you have a fair amount of light around the blind. This means that vertical bllinds will often be used in partnership with curtains. So when the two are combined the end result is satisfactory.

We don’t recommend a vertical for outside recess face fix mount as a blackout option.

The make-up of a venetian blind allows for a close fit to the inside of the recess, similar to that of the Roman and pleated blind ­– as long as the window is nice and square, allowing for 1cm clearance fit.

The slats overlap each other, so this will allow a little light to penetrate through the overlaps. But since they are a solid material no light filters through the slats themselves.

The slats are all held together with a nylon ladder cord that travels through the slats to tilt and raise the blind, so the holes punched into the slats to take the cord will allow light to bleed into the room. This, combined with the overlaps, allows some amount of light to enter the room.

The bigger the slat size then the darker the blind will be in the closed position due to smaller quantity of slats, so there are fewer overlaps.

Outside face fix mount we would suggest allowing a minimum of 8cm extra to the width but the advantage of this would be questionable over inside mount.

Blockability score – Venetian blind 7 out of 10

Wooden venetian 50mm Valley Oak

Summary:

Use the information we have presented to decide how much light is acceptable. Are you a light or heavy sleeper, and what style of blind is most likely to suit the room.